Autolyse: In a large mixing bowl, combine whole wheat flour, bread flour and water. Using a wooden spoon or spatula, stir the ingredients together until no traces of dry flour remain. Cover the bowl with plastic wrap, set in a warm place and let the dough rest for 1 hour.

Prepare the inclusions: Using an apple peeler, strip the rind off of 1 lemon, but be careful not peel too deeply into the bitter white pith. Finely chop the rind and set aside.

Add the starter and inclusions: Add the sourdough starter, salt, dried rosemary and lemon peel to the autolysed dough. Fold the dough over the sourdough starter and the inclusions until fully incorporated. Cover the bowl with plastic wrap and set in a warm place for 30 minutes.

Strengthen the dough: Perform a coil fold by picking the center of the dough with your fingertips. Lift the dough until the ends release from the bowl. Turn the bowl 90 degrees and perform another coil fold. Transfer the dough to a clean, lightly-oiled bowl, cover with plastic wrap and set in a warm place for 30 minutes.

Working in the bowl, complete 3 to 4 more sets of coil folds in 30 minute intervals. Cover the bowl with plastic wrap and set in a warm place after each fold. Once the dough looks smooth and feels strong, let the dough rest untouched for 1 hour.

Shape the dough: Shape the dough into a boule or a batard. Cover the bowl with plastic wrap.

Cold proof: Place the dough in the refrigerator to proof overnight.

Prep: Preheat the oven to 500 F with a Dutch oven inside.

Score the dough: Turn the dough out onto a piece of parchment paper. Cut a large gash on the dough at least ¼ to ½ inch deep.

Bake: Transfer the dough into the Dutch oven with the parchment paper. Bake covered for 25 to 30 minutes and uncovered for 10 to 15 minutes, depending on how dark you’d like the crust.

Serve: Transfer the bread to a wire rack and allow it to cool for at least 2 hours before slicing.

Store: Store any leftover slices of sourdough in a ziplock bag at room temperature for up to 3 days.